A known electric pump is disclosed in JP2014-181780A (hereinafter referred to as Patent reference 1). Patent reference 1 discloses a technology that operates an electric oil pump under conditions where an oil temperature level detected by an oil temperature sensor is equal to or higher than a predetermined temperature level. The electric pump disclosed in Patent reference 1 directly detects the temperature level of oil by including the oil temperature sensor within an oil pan of an engine.
A vehicle including an engine is widely used, the vehicle being provided with an oil pump that supplies oil (lubricant) of an oil pan of the engine to an oil pressure actuator or to a main gallery of the engine.
The temperature level of oil reserved in the oil pan of the engine may be low, and the viscosity of the oil may be high. The oil may not be supplied appropriately even if the oil pump operates to rotate with a normal rotary speed because of the low temperature level of the oil. From this reason, according to Patent reference 1, the operation mode of the oil pump is set in response to the oil temperature level detected by the oil temperature sensor.
Here, regarding to the detection mode of the oil temperature level detected by the oil temperature sensor, for example, the assembling and wiring of the oil temperature sensor take a certain amount of time and effort in a case where the oil temperature sensor that comes in contact with the oil reserved in the oil pan is used. In addition, in a case where the oil temperature sensor coming in contact with the oil is used, the oil temperature level of the oil pan is precisely detected, whereas the oil temperature level of an inside of the oil pump cannot be detected.
That is, in a case where the temperature level of the oil pump is low, the temperature level of the oil supplied to the oil pump may decrease within the oil pump and the viscosity of oil may increase even after the temperature level of the oil increases in response to the operation of the engine. From this reason, the detection of the temperature level of the inside of the oil pump is important. After the oil pump starts operating, the oil temperature level of the inside of the oil pump is desired to be detected precisely by a removal of the influence of the heat generated in response to the operation of the pump.
A need thus exists for an electric pump which is not susceptible to the drawback mentioned above.